I went back 3 years, I could keep going but that is as far as I could go on short notice, and could not find a single 7 week stretch where the number 1 team going into that week lost every single week in that stretch. I could not find it. Last week being particularly murky as the top 3 all lost. Now it is going to be KC as the number 1 team again. They are playing Denver so that should be an easy game but the Cardinals should have been easy for the Cowboys and the Jets easy for KC and Philadelphia (and the Bills if we are being honest because their struggles are obvious in that they lost the 2 best players on their defense but that was post Wilson beating them).
Teams being upset is not surprising. It happens every week and there are elements that make it slightly easier to predict (Browns own the Bengals as an example) but I cannot find a single example where the number 1 team just kept losing over and over and over again. Usually a team on top stays there for a couple weeks then gets knocked down then a new team stays up for a couple then gets knocked down.